Flash lamp with mirror

ABSTRACT

In a flash lamp, a mirror structure ( 20, 30, 40 ) is fixed at an inner end portion of an exhaust pipe ( 21, 34, 44 ) secured to a center of a stem ( 6 ) disposed at a bottom portion of an envelope (H). An arc emission part (S) is located at a focal position of a rounded mirror surface  24.

TECHNICAL FIELD

The present invention relates to a flash lamp equipped with a mirror,utilized as a light source for spectroscopy, emission analysis or thelike, a stroboscopic light source, a light source for processinghigh-quality images, or the like.

BACKGROUND ART

A conventional technique in such a field is disclosed in Japanese PatentPublication No. HEI 7-120518. In the mirror-equipped f lash lampdescribed in the above-mentioned publication, a cathode and an anode aredisposed facing each other inside a bulb made of glass, the front end ofa trigger probe electrode is located between the cathode and the anode,and an inert gas, such as xenon or argon, is encapsulated in the bulb.Further, for attaining high-output light, an ellipsoidal mirror isdisposed inside the bulb, and the cathode is inserted in an openingformed in the bottom part of the ellipsoidal mirror, whereby an arcemission point is formed at a first focal point inside the ellipsoidalmirror. By the provision of such an ellipsoidal mirror inside the bulb,a high-output flash lamp is produced.

DISCLOSURE OF THE INVENTION

Due to the above-mentioned configuration, however, the following problemexists in the conventional mirror-equipped flash lamp.

Namely, since the bottom part of the ellipsoidal mirror is formed withan opening, light reflected by the ellipsoidal mirror forms a darkportion in its irradiation area under the influence of the opening, thuslacking uniformity. As a result, when irradiation light is to beintroduced into a small-diameter fiber or slit, there have been caseswhere shortages or inconsistencies in quantity of light occur. WhileJapanese Patent Publication No. SHO 56-50384 also discloses a xenon lampequipped with a mirror, the mirror in this case is also formed with anopening for receiving a pedestal for supporting an electrode.

For solving the above-mentioned problem, it is an object of the presentinvention, in particular, to provide a mirror-equipped flash lampadapted to generate uniform light whose irradiation inconsistencies arevery small.

The mirror-equipped flash lamp in accordance with the present inventionis a flash lamp in which an arc emission is generated by cooperation ofa cathode, an anode, a trigger probe electrode, and a sparker electrodewhich are secured by way of stem pins to a stem disposed in an envelopehaving a light projection window, and this emission is emitted from thelight projection window; wherein a mirror structure, contained in theenvelope, having a rounded mirror surface facing the light projectionwindow is contained in the envelope between a stem pin for the cathodeand a stem pin for the anode and is secured to a leg rising from thestem, the mirror structure and an exhaust port of an exhaust pipesecured to a center of the stem are separated from each other, and anarc emission part is disposed at a focal position of the rounded mirrorsurface.

In this mirror-equipped flash lamp, when a predetermined voltage isapplied between the cathode and the anode, and a trigger voltage isapplied to the trigger probe electrode and the sparker electrode, adischarge occurs at the trigger probe electrode and, along with thisdischarge, a main discharge of an arc occurs between the cathode and theanode. The resulting emission is reflected by the mirror surface, so asto be emitted from the light projection window. Since such a mirrorsurface is formed as a rounded mirror surface, and a mirror structure iscontained between a stem pin for the cathode and a stem pin for theanode, it is not necessary to bore a hole in the rounded mirror surface,the whole mirror surface can be used effectively as a reflectingsurface, the reflection characteristics inherent in the mirror surfacecan fully be utilized, and the arc emission part can be placed at thefocal position of the rounded mirror surface while preventing the stempins from penetrating through the rounded mirror surface. Also, sincethe exhaust port of the exhaust pipe and the mirror structure areseparated from each other, the exhaust port of the exhaust pipe facinginside the envelope would not be closed by the mirror structure.

Preferably, in this case, the mirror structure comprises a mirrorportion made of glass having the rounded mirror surface, and a mirrorholder surrounding the mirror portion. When such a configuration isemployed, in the forming of the rounded mirror surface, the surfaceprocessing is easier than that in metals such as aluminum, therebyyielding a surface which not only can be made at a lower manufacturingcost but also has a low surface roughness and high surface precision.Also, when aluminum is vapor-deposited on a glass surface to form arounded mirror -surface, a firm specular surface would be formed on theglass surface, whereby a highly durable rounded mirror surface can beobtained.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view of an embodiment of the mirror-equipped flash lampin accordance with the present invention;

FIG. 2 is a sectional view taken along the line II—II of FIG. 1;

FIG. 3 is a sectional view showing the mirror structure and exhaust pipeemployed in the flash lamp shown in FIG. 1; and

FIG. 4 is a sectional view showing a modified example of the mirrorstructure.

BEST MODE FOR CARRYING OUT THE INVENTION

In the following, preferred embodiments of the mirror-equipped flashlamp in accordance with the present invention will be explained indetail with reference to the drawings.

FIG. 1 is a plan view showing the appearance of a mirror-equipped flashlamp in accordance with the present invention, whereas FIG. 2 is asectional view taken along the line II—II of FIG. 1. The mirror-equippedflash lamp 1 shown in these drawings has a cylindrical side tube 2 madeof covar metal, a circular first opening 3 is formed at one end of theside tube 2, and a light projection window 4 made of sapphire glass issecured to the side tube 2 so as to close the first opening 3. Further,a circular second opening 5 is formed at the other end of the side tube2, and a disk-shaped stem 6 made of covar glass is secured to the sidetube 2 so as to close the second opening 5. Also, a cylindrical stemholder 7 made of covar metal is fused to the peripheral side face of thestem 6, so that the flange portion 7 a of the stem holder 7 and theflange 2 a of the side tube 2 can be arc-welded to each other, therebymaking it easier for the stem 6 and the side tube 2 to be secured toeach other. Thus, a hermetic type envelope H of the flash lamp 1 isconstructed.

Further, a cathode 8 and an anode 9 which are adapted to cause an arcdischarge are disposed inside the envelope H, the cathode 8 is fixed atthe front end of a stem pin 10 which is secured so as to penetratethrough the stem 6 and extends in the tube axis direction, and this stempin 10 is covered with an electrically insulating pipe 10 a made ofceramics. Similarly, the anode 9 is fixed at the front end of a stem pin11 which is secured so as to penetrate through the stem 6 and extends inthe tube axis direction, and is covered with an electrically insulatingpipe 11 a made of ceramics. The cathode 8 and the anode 9 are positioneddirectly below the light projection window 4, and oppose each other on aline in the horizontal direction (direction perpendicular to the tubeaxis). Also, an arc emission part S formed between the front end of thecathode 8 and the front end of the anode 9 is caused to align with thetube axis.

Also, inside the envelope H, two trigger probe electrodes 12, 13 aredisposed such that their front ends are located between the cathode 8and the anode 9, whereas these electrodes 12, 13 are secured to the stem6 with the aid of stem pins 14, 15. Further, a sparker electrode 16 isdisposed inside the envelope H, and is secured to the stem 6 with theaid of a stem pin 17. The inside of the envelope H is kept at a highpressure, with xenon gas as an example of the inert gas beingencapsulated therein.

When a predetermined voltage is applied between the cathode 8 and theanode 9 by way of the cathode stem pin 10 and anode stem pin 11, and atrigger voltage is applied to the trigger probe electrodes 12, 13 andthe sparker electrode 16 by way of the stem pins 14, 15, 17, a dischargeoccurs at the trigger probe electrodes 12, 13 and, along with thisdischarge, a main discharge of an arc occurs between the cathode 8 andthe anode 9. The emission at this time is reflected by a mirrorstructure 20 which will be explained later, so as to be emitted from thelight projection window 4.

As shown in FIG. 3, this mirror structure 20 has a metal substrate 22made of aluminum, copper, or the like, which is formed like a dish. Thetop face of the substrate 22 is formed with a mirror surface 24, facingthe light projection window 4, shaped into a rounded mirror surfacewhile constituting a concave mirror. Here, the rounded mirror surfacerefers to a mirror surface made of a curved surface with a constantradius of curvature having a single focal point. This rounded mirrorsurface 24 is formed by vapor-depositing aluminum onto the metalsubstrate 22. When the rounded mirror surface 24 is employed, the arcemission part S (see FIG. 2) located between the cathode 8 and the anode9 can align with the focal position (center of curvature) of the mirrorsurface 24, thus allowing the mirror surface 24 to reliably collectlight.

As shown in FIG. 2, the mirror structure 20 is disposed between the arcemission part S and the stem 6 and is contained between the cathode stempin 10 and the anode stem pin 11, so as to be positioned directly belowthe arc emission part S. For enabling such an arrangement, the mirrorstructure 20 is fixed at the front end of each of pin-shaped legs 23embedded in the stem 6. Specifically, an L-shaped front end portion(inner end portion) 23 a of each leg 23 is secured to the bottom face 22a of the substrate 22 of the mirror structure 20 by welding.

Further, an exhaust pipe 21 made of covar metal is disposed between thelegs 23, and extends in the tube axis direction so as to penetratethrough the center of the disk-shaped stem 6. Also, the exhaust port 21a of the exhaust pipe 21 projects so as to open inside the envelope H,and is disposed at a position separate from the mirror structure 20,whereby the exhaust port 21 a of the exhaust pipe 21 facing inside theenvelope H would not be closed by the mirror structure 20. Therefore, atthe time of assembling the flash lamp 1, the operations of dischargingthe air from inside the envelope H and introducing an inert gas (e.g.,xenon gas) into the envelope H can reliably be achieved by the exhaustport 21 a.

When such a configuration is employed, the rounded mirror surface 24 canbe made as a complete surface without necessitating an opening to beformed therein. Thus, post-processing such as boring a hole in therounded mirror surface 24 is not necessary, the whole rounded mirrorsurface 24 can be used effectively as a reflecting surface, and thereflection characteristics inherent in the rounded mirror surface 24 canfully be utilized.

Another embodiment of the mirror-equipped flash lamp in accordance withthe present invention will now be explained in brief. Here, constituentsidentical or equivalent to those in the above-mentioned embodiment willbe referred to with numerals or letters identical to each other.

As shown in FIG. 4, the mirror structure 30 is constructed as adividable type and has a cup-shaped mirror holder 32 made of stainless,and this mirror holder 32 is formed like a cylinder having a bottom face32 a to which an L-shaped front portion (inner end portion) 23 a of eachleg 23 is secured by welding. A disk-shaped mirror portion 33 is tightlyfitted in the mirror holder 32 in a concentric fashion. The mirrorportion 33 is made of a glass material and has such a diameter that itcan be inserted into the mirror holder 32 from its opening 32 c. Also, arounded mirror surface 34 facing the light projection window 4 is formedat the top face of the mirror portion 33 and constitutes a concavemirror. Here, the rounded mirror surface refers to a mirror surface madeof a curved surface with a constant radius of curvature having a singlefocal point. This rounded mirror surface 34 is formed byvapor-depositing aluminum onto a glass surface.

When glass is thus employed in the mirror portion 33, in the forming ofthe rounded mirror surface 34, the surface processing is easier thanthat in metals such as aluminum, thereby yielding the rounded mirrorsurface 34 which not only can be made at a lower manufacturing cost butalso has a low surface roughness and high surface precision. Also, whenaluminum is vapor-deposited on glass to form the rounded mirror surface34, a firm specular surface would be formed, whereby the highly durablerounded mirror surface 34 can be obtained. With the aid of an adhesive,the mirror portion 33 made of glass is secured to the mirror holder 32made of a metal. When an unshown ring body or pawl piece is utilized,however, the mirror portion 33 is held within the mirror holder 32 asbeing pressed from thereabove.

The present invention is not limited to the above-mentioned variousembodiments. For example, the legs 23 may be shaped like a leaf insteadof a pin. Further, the mirror portion 33 may be constructed so as to beembedded in the mirror structure 20.

As a consequence of the foregoing configuration, the mirror-equippedflash lamp in accordance with the present invention can yield thefollowing effects. Namely, since a mirror structure having a roundedmirror surface, contained in an envelope, facing a light projectionwindow is contained between a stem pin for a cathode and a stem pin foran anode inside the envelope and is secured to a leg rising from a stem,while the mirror structure and an exhaust port of an exhaust pipesecured to a center of the stem are separated from each other, an arcemission part being disposed at a focal position of the rounded mirrorsurface, a structure in which the rounded mirror surface is free ofholes can be attained, and uniform light can be generated with verysmall irradiation inconsistencies.

Industrial Applicability

The mirror-equipped flash lamp in accordance with the present inventioncan be utilized as a light source for spectroscopy, emission analysis orthe like, a stroboscopic light source, a light source for processinghigh-quality images, or the like.

What is claimed is,:
 1. A flash lamp comprising: an exhaust pipepenetrating through a stem of an envelope; a pair of stem pins extendingfrom said stem; a mirror structure, disposed between said stem pins andsecured to said stem, having a concave mirror for reflecting an arcemission between an anode and a cathode respectively supported by saidstem pins and emitting said emission from a window of said envelope,said concave mirror being disposed between an inner end portion of saidexhaust pipe and said window; and a sparker electrode disposed insidesaid envelope for causing a discharge, said sparker electrode beinglocated at a point outside of a space bounded by the concave surface ofsaid concave mirror and said window.
 2. A flash lamp according to claim1, wherein said mirror structure comprises a mirror portion made ofglass having said concave mirror, and a mirror holder surrounding saidmirror portion.
 3. A flash lamp according to claim 1, wherein saidsparker electrode is secured to said stem with an aid of a stem pin. 4.A flash lamp according to claim 1, wherein the flash lamp is configuredsuch that, when a predetermined voltage is applied between said cathodeand said anode, and a trigger voltage is applied to trigger probeelectrodes arranged in said envelope and said sparker electrode, adischarge occurs at the trigger probe electrodes and, along with thisdischarge, a main arc discharge occurs between said cathode and saidanode.
 5. A flash lamp comprising: an exhaust pipe penetrating through astem of an envelope; a pair of stem pins extending from said stem; and amirror structure, disposed between said stem pins and secured to saidstem, having a concave mirror for reflecting an arc emission between ananode and a cathode respectively supported by said stem pins andemitting said emission from a window of said envelope, said concavemirror being disposed between an inner end portion of said exhaust pipeand said window, the mirror structure comprising a mirror portion madeof glass having said concave mirror and a mirror holder surrounding saidmirror portion.